Systems exist for the parallel synthesis of various chemical compounds in microtiter plate format. Accordingly, many liquid handling systems have been developed for automated parallel synthesis in conjunction with such microtiter plate formats. High throughput liquid chromatography/mass spectrometry systems capable of isolating compounds on the basis of their molecular weight have also been developed. However, a system for easily and efficiently determining the total collected masses of compounds which are fraction collected in microtiter plate format has proven elusive.
In general, existing high throughput liquid chromatography/mass spectrometry systems isolate compounds by fractionation into fraction collector tubes which are individually removable from a rack. Numerous problems exist when attempting to quantify the total mass of each of the compounds collected in the various fraction collector tubes. First, each tube in the rack needs to be individually removed, weighed and its weight recorded. The compounds are then fraction collected into the individual tubes in the rack. Subsequent to fraction collection, the tubes are removed one after another from the rack and are placed in a device which concentrates them down by drying the contents of the tube. After the contents of the tube have been concentrated down by drying, the dried tubes are individually re-weighed and the net weight of each sample in the fraction collection tubes is then determined by comparing the initial weight of the empty tube with the weight of the tube with the dried compound therein. The weight information so determined allows the compounds to be redissolved with a volatile solvent to a desired set point molarity. The tubes are then placed into a rack and an aliquot is delivered into a microtiter plate for use in a biological assay.
In high throughput synthesis operations, the number of samples can be quite large so the operation of separately weighing, re-weighing, tracking, and labeling a very large number of fraction collector tubes becomes quite cumbersome. Moreover, when weighing and re-weighing relatively small volume fluid samples, inaccuracies in the weight of the tubes themselves may account for larger weight differences than the weight of the compound fraction collected therein. As such, significant errors can be introduced to the net weight of each collected compound, and its final concentration upon dissolution. In addition, special devices such as racks and an apparatus for concentrating down fluid samples have to be used with the dried down products later having to be reformatted into a microtiter plate format.